1. Field of the Invention
The invention relates to a decorative lighting device, more particularly to a decorative lighting device that has enhanced heat-isolation and waterproof effects.
2. Description of the Related Art
As shown in FIG. 1 and FIG. 2, a conventional decorative lighting device 1 includes a light-emitting unit 11, a holding unit 12, and two electric wires 13.
The light-emitting unit 11 includes a plug-in base 112 and a light bulb 111. The plug-in base 112 is made from an insulating material, and includes upper and lower bodies 113, 114 disposed opposite to each other along an axis (X1). The upper body 113 defines a bulb-receiving space 118. The lower body 114 includes a lateral guiding wall 116 extending downwardly from the upper body 113 along the axis (X1). The light bulb 111 has a lower bulb portion 117, and two lead-in wires 115 which extend downwardly and outwardly of the lower bulb portion 117, and which are configured such that when the lower bulb portion 117 is inserted into the bulb-receiving space 118, the two lead-in wires 115 extend downwardly and outwardly of the upper body 113 of the plug-in base 112 to have the lateral guiding wall 116 interposed therebetween.
The holding unit 12 is made from an insulating material (e.g., plastic), extends downwardly along the axis (X1), and includes a holding body 122 which confines a holding space 125, and two electrical terminals 121. The two electrical terminals 121 are disposed to be secured to an inner wall surface 123 of the holding body 122 such that once the lower body 114 of the plug-in base 112 is brought to be fitted into the holding space 125 by virtue of sliding movement of the lateral guiding wall 116 relative to the inner wall surface 123, the two lead-in wires 115 are brought into electrical contact with the two electrical terminals 121, respectively.
The two electric wires 13 extend into the holding space 125 and are in electrical contact with the two electrical terminals 121, respectively.
As shown in FIG. 2, the holding body 122 of the holding unit 12 is configured such that when the plug-in base 112 of the light-emitting unit 11 is received in the holding space 125, while the electric wires 13 extend into the holding space 125, the plug-in base 12 and the electric wires 13 are placed securely in the holding space 125 so as to prevent water from entering thereinto, and so as to ensure good electrical contact among the two lead-in wires 115, the two electrical terminals 121, and the two electric wires 13.
A plurality of the conventional decorative lighting devices 1 can be connected in series to form a lamp assembly (not shown) to facilitate decorative applications. When one of the conventional decorative lighting devices 1 in the lamp assembly is damaged due to long-term usage or other reasons, electric current flowing through the rest of the conventional decorative lighting devices 1 (i.e., the non-damaged conventional decorative lighting devices) increases accordingly. However, as the electric current flowing through the conventional decorative lighting device 1 increases, heat dissipation increases in a square function, resulting in an increase in temperature that can easily over heat the light bulb 111. Under this situation, there is a greater possibility for the non-damaged conventional decorative lighting devices 1 to break down. In addition, when the holding unit 12, which is made from an insulating material, gets in contact with one of the overheated non-damaged conventional decorative lighting devices 1, the holding unit 12 can melt easily, exposing the electrical terminals 121, and putting individuals who accidentally touch the exposed electrical terminals 121 in danger. Therefore, the conventional decorative lighting device 1 does not meet the safety standards set out by Underwriters Laboratories Inc., and is in need of improvements.